The verification probe of this invention is designed for the nondestructive testing of a fastener to determine if the fastener has been properly installed on a workpiece. Preferably, the fastener is of the type having a thread cylinder which communicates with an axially aligned opening in the workpiece, such as for example, a self-piercing nut as disclosed in U.S. Pat. No. 3,648,747 assigned to the assignee of the instant application. The pierce nut includes a pilot portion which pierces an opening in a panel, a pair of flanges on opposed sides of the pilot having panel-bearing faces and re-entrant grooves in the flangebearing surfaces adjacent the pilot. Upon forced engagement with the panel, the pilot pierces an opening in the panel and the pierced panel edges are deformed into and retained by the re-entrant grooves.
Typically, several fasteners of the above type will be simultaneously pressed into a part as the part is being formed. Each fastener must be properly installed which requires it to be properly positioned on the panel, the slug formed by the fastener to be discharged from the thread cylinder and the fastener to have a minimum retention capability.
There are no devices or processes available that perform all three checks for proper installation in one operation, that is, checking to verify slug removal, proper location and minimum retention. Nor are there any that perform all three checks on every fastener individually.
Applicant is aware of only three methods presently used to test fasteners. The first method involves randomly selecting a part from a batch of parts and striking one or more fasteners with a hammer. The force used to strike the fastener is determined by the person doing the test to be within the desired retention force of the fastener. Obviously, this is a very imprecise method. Further, it doesn't determine the proper location of the part or verify removal of the slug or test every fastener on every part.
In the second test, a part is selected from a batch of parts and a hydraulic cylinder is used to apply force to the fastener until the fastener releases, from the part. If the applied force is within a predetermined range, the batch of parts is considered to be good. If not, further testing may be required and the result may be the rejection of an entire batch of parts. Again, the second method does not test each fastener on each part and does not test for the proper positioning of the fastener on the part. Further, this test is a destructive test requiring the destruction of at least one fastener and, therefore, one part.
The last known method uses fiber-optics and television systems to test for the proper location of the fastener and to verify that the slug has been removed. Of course, this method does not test for retention requiring one of the above tests to be used.
As indicated earlier, in order for a part to be good, every fastener must be properly installed, which requires the fastener to be properly positioned and properly attached. None of the known methods of testing provide for the non-destructive testing of every fastener in one operation.